Digital cameras have recently been wide spread, which are imaging apparatuses that takes image data through a solid state imaging device like a CCD image sensor, and records it. The digital cameras are provided with a flash device to project a flashlight toward a subject at the exposure when brightness of the subject is in a low level.
If, however, the subject is so distant that the flashlight cannot reach it, the subsequent image will be under-exposed. To solve this problem, a digital camera has been known for example from Japanese Laid-open Patent Application No. Hei 06-121225, wherein the image signal outputted from the solid state imaging device is amplified with a gain that is changed according to the object distance, to compensate for a shortage of exposure amount.
Also a digital camera has been known for example from Japanese Laid-open Patent Application No. 2000-134533, wherein an imaging sensitivity and a light control value, which is a reference value for stopping emission of the flashlight, are decided based on the object distance on making a flash shot. The digital camera of this prior art extends the range of object distance, within which the volume of flashlight is automatically controllable.
In a digital camera as disclosed for example in Japanese Laid-open Patent Application No. Hei 11-084489, several times of preliminary exposures are made with a corresponding number of preliminary light emissions at a constant light volume, and respective image signals obtained by the preliminary exposures are amplified with different gains from each other. A flashlight volume for a main or final exposure is decided based on the amplified image signals, while checking if any of the amplified image signals are within a predetermined signal level range.
However, since the digital cameras as disclosed in the above-mentioned first and second prior arts decide the imaging sensitivity and the light control value of the flash device merely based on the object distance, it has been different to control the flashlight volume properly. This is because the flashlight reaching range depends not only upon the object distance but also upon the f-number of the lens. The third prior art, as requiring making several preliminary light emissions, takes a long time for one shooting operation.
In view of the foregoing problems, an object of the present invention is to provide an imaging apparatus that can make the shooting operation promptly with a proper flashlight volume to obtain a properly exposed image. Another object of the present invention is to provide an exposure control method for such an imaging apparatus.